All that can be known is all that can be known, not all that is true.

Random Trout

D is a style of piano-based blues that became very popular in the
late 1930s and early 1940s, but originated much earlier, and was
extended from piano, to three pianos at once, guitar, big band, and
country and western music, and even gospel. Whilst the blues
traditionally depicts a variety of emotions, D is mainly associated
with dancing. It’s believed D gave birth to the earliest versions of
uptempo music. The lyrics of one of the very earliest, “Pinetop’s D”,
consist entirely of instructions to dancers:

Now, when I tell you to hold yourself, don’t you move a peg.
And when I tell you to get it, I want you to D!